Methods For Manufacturing And Assembling Dual Material Tissue Interface For Negative-Pressure Therapy

ABSTRACT

A dressing for treating tissue with negative pressure may be a composite of dressing layers, including a release film, perforated gel layer, a perforated polymer film, a manifold, and an adhesive cover. A method of manufacturing the dressing may comprise providing a first layer, such as the gel layer, on a substrate, perforating the first layer on the substrate to create a plurality of apertures in the first layer, and creating an index of the plurality of apertures in the first layer. A laser can be calibrated based on the index. A second layer, such as the polymer film, may be coupled to the first layer, and a plurality of slots can be cut in the second layer with the laser. Each of the slots can be cut through one of the apertures in the first layer based on the index.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/876,299, filed May 18, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/997,931, entitled “Methods for Manufacturing andAssembling Dual Material Tissue Interface for Negative-PressureTherapy,” filed Jun. 5, 2018, which claims the benefit, under 35 U.S.C.§ 119(e), of the filing of U.S. Provisional Patent Application No.62/623,325, entitled “Methods For Manufacturing And Assembling DualMaterial Tissue Interface For Negative-Pressure Therapy,” filed Jan. 29,2018; U.S. Provisional Patent Application No. 62/616,244, entitled“Composite Dressings For Improved Granulation And Reduced MacerationWith Negative-Pressure Treatment,” filed Jan. 11, 2018; U.S. ProvisionalPatent Application No. 62/615,821, entitled “Methods For ManufacturingAnd Assembling Dual Material Tissue Interface For Negative-PressureTherapy,” filed Jan. 10, 2018; U.S. Provisional Patent Application No.62/613,494, entitled “Peel And Place Dressing For Thick Exudate AndInstillation,” filed Jan. 4, 2018; U.S. Provisional Patent ApplicationNo. 62/592,950, entitled “Multi-Layer Wound Filler For Extended WearTime,” filed Nov. 30, 2017; U.S. Provisional Patent Application No.62/576,498, entitled “Systems, Apparatuses, And Methods ForNegative-Pressure Treatment With Reduced Tissue In-Growth,” filed Oct.24, 2017; U.S. Provisional Patent Application No. 62/565,754, entitled“Composite Dressings For Improved Granulation And Reduced MacerationWith Negative-Pressure Treatment,” filed Sep. 29, 2017; U.S. ProvisionalPatent Application No. 62/516,540, entitled “Tissue Contact Interface,”filed Jun. 7, 2017; U.S. Provisional Patent Application No. 62/516,550,entitled “Composite Dressings For Improved Granulation And ReducedMaceration With Negative-Pressure Treatment” filed Jun. 7, 2017; andU.S. Provisional Patent Application No. 62/516,566, entitled “CompositeDressings For Improved Granulation And Reduced Maceration WithNegative-Pressure Treatment” filed Jun. 7, 2017, each of which areincorporated herein by reference for all purposes.

TECHNICAL FIELD

The invention set forth in the appended claims relates generally totissue treatment systems and more particularly, but without limitation,to methods of manufacturing a dual material tissue interface fornegative-pressure therapy.

BACKGROUND

Clinical studies and practice have shown that reducing pressure inproximity to a tissue site can augment and accelerate growth of newtissue at the tissue site. The applications of this phenomenon arenumerous, but it has proven particularly advantageous for treatingwounds. Regardless of the etiology of a wound, whether trauma, surgery,or another cause, proper care of the wound is important to the outcome.Treatment of wounds or other tissue with reduced pressure may becommonly referred to as “negative-pressure therapy,” but is also knownby other names, including “negative-pressure wound therapy,”“reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,”and “topical negative-pressure,” for example. Negative-pressure therapymay provide a number of benefits, including migration of epithelial andsubcutaneous tissues, improved blood flow, and micro-deformation oftissue at a wound site. Together, these benefits can increasedevelopment of granulation tissue and reduce healing times.

There is also widespread acceptance that cleansing a tissue site can behighly beneficial for new tissue growth. For example, a wound or acavity can be washed out with a stream of liquid solution fortherapeutic purposes. These practices are commonly referred to as“irrigation” and “lavage” respectively. “Instillation” is anotherpractice that generally refers to a process of slowly introducing fluidto a tissue site and leaving the fluid for a prescribed period of timebefore removing the fluid. For example, instillation of topicaltreatment solutions over a wound bed can be combined withnegative-pressure therapy to further promote wound healing by looseningsoluble contaminants in a wound bed and removing infectious material. Asa result, soluble bacterial burden can be decreased, contaminantsremoved, and the wound cleansed.

While the clinical benefits of negative-pressure therapy and/orinstillation therapy are widely known, improvements to therapy systems,components, and processes may benefit healthcare providers and patients.

BRIEF SUMMARY

New and useful systems, apparatuses, and methods for treating tissue ina negative-pressure therapy environment are set forth in the appendedclaims. Illustrative embodiments are also provided to enable a personskilled in the art to make and use the claimed subject matter.

For example, in some embodiments, a dressing for treating tissue may bea composite of dressing layers including a release film, perforated gellayer, a perforated polymer film, a manifold, and an adhesive cover. Themanifold may be reticulated foam in some examples, and may be relativelythin and hydrophobic to reduce the fluid hold capacity of the dressing.The manifold may also be thin to reduce the dressing profile andincrease flexibility, which can enable it to conform to wound beds andother tissue sites under negative pressure. In some embodiments, theperforations may be slits or slots.

The perforation pattern of the polymer film can be aligned with theperforation pattern of at least a central area of the gel layer. Forexample, in some embodiments, the gel layer may be perforated andindexed on a liner, and the polymer film can loaded and fixed to the gellayer. The combined laminate can be presented to a laser. The positionof a laser mask can be calibrated to an underside of the dressing,referencing perforations in the gel layer to calibrate its position. Thelaser can then be fired, creating centrally registered slots in thepolymer film within the perforations of the gel layer.

More generally, a method of manufacturing a dressing fornegative-pressure treatment may comprise providing a first layer, suchas the gel layer, on a substrate, perforating the first layer on thesubstrate to create a plurality of apertures in the first layer, andcreating an index of the plurality of apertures in the first layer. Alaser can be calibrated based on the index. A second layer, such as thepolymer film, may be coupled to the first layer, and a plurality ofslots can be cut in the second layer with the laser. Each of the slotscan be cut through one of the apertures in the first layer based on theindex.

Objectives, advantages, and a preferred mode of making and using theclaimed subject matter may be understood best by reference to theaccompanying drawings in conjunction with the following detaileddescription of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of an example embodiment of atherapy system that can provide negative-pressure treatment andinstillation treatment in accordance with this specification;

FIG. 2 is a graph illustrating additional details of example pressurecontrol modes that may be associated with some embodiments of thetherapy system of FIG. 1;

FIG. 3 is a graph illustrating additional details that may be associatedwith another example pressure control mode in some embodiments of thetherapy system of FIG. 1;

FIG. 4 is an assembly view of an example of a dressing that may beassociated with some embodiments of the therapy system of FIG. 1;

FIG. 5 is a schematic view of an example of a polymer film illustratingadditional details that may be associated with some embodiments of thedressing of FIG. 4;

FIG. 6 is a schematic view of an example configuration of apertures thatmay be associated with some embodiments of the dressing of FIG. 4;

FIG. 7 is a schematic view of an example of a layer having theconfiguration of apertures of FIG. 6 overlaid on the polymer film ofFIG. 5; and

FIG. 8 is a flow diagram illustrating an example method of manufacturingsome components of dressings that may be associated with the therapysystem of FIG. 1.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The following description of example embodiments provides informationthat enables a person skilled in the art to make and use the subjectmatter set forth in the appended claims, but may omit certain detailsalready well-known in the art. The following detailed description is,therefore, to be taken as illustrative and not limiting.

The example embodiments may also be described herein with reference tospatial relationships between various elements or to the spatialorientation of various elements depicted in the attached drawings. Ingeneral, such relationships or orientation assume a frame of referenceconsistent with or relative to a patient in a position to receivetreatment. However, as should be recognized by those skilled in the art,this frame of reference is merely a descriptive expedient rather than astrict prescription.

FIG. 1 is a simplified functional block diagram of an example embodimentof a therapy system 100 that can provide negative-pressure therapy withinstillation of topical treatment solutions to a tissue site inaccordance with this specification.

The term “tissue site” in this context broadly refers to a wound,defect, or other treatment target located on or within tissue,including, but not limited to, a surface wound, bone tissue, adiposetissue, muscle tissue, neural tissue, dermal tissue, vascular tissue,connective tissue, cartilage, tendons, or ligaments. A wound may includechronic, acute, traumatic, subacute, and dehisced wounds,partial-thickness burns, ulcers (such as diabetic, pressure, or venousinsufficiency ulcers), flaps, and grafts, for example. A surface wound,as used herein, is a wound on the surface of a body that is exposed tothe outer surface of the body, such as an injury or damage to theepidermis, dermis, and/or subcutaneous layers. Surface wounds mayinclude ulcers or closed incisions, for example. A surface wound, asused herein, does not include wounds within an intra-abdominal cavity.The term “tissue site” may also refer to areas of any tissue that arenot necessarily wounded or defective, but are instead areas in which itmay be desirable to add or promote the growth of additional tissue. Forexample, negative pressure may be applied to a tissue site to growadditional tissue that may be harvested and transplanted.

The therapy system 100 may include a source or supply of negativepressure, such as a negative-pressure source 105, a dressing 110, afluid container, such as a container 115, and a regulator or controller,such as a controller 120, for example. Additionally, the therapy system100 may include sensors to measure operating parameters and providefeedback signals to the controller 120 indicative of the operatingparameters. As illustrated in FIG. 1, for example, the therapy system100 may include a first sensor 125 and a second sensor 130 coupled tothe controller 120. As illustrated in the example of FIG. 1, thedressing 110 may comprise or consist essentially of a tissue interface135, a cover 140, or both in some embodiments.

The therapy system 100 may also include a source of instillationsolution. For example, a solution source 145 may be fluidly coupled tothe dressing 110, as illustrated in the example embodiment of FIG. 1.The solution source 145 may be fluidly coupled to a positive-pressuresource such as the positive-pressure source 150, a negative-pressuresource such as the negative-pressure source 105, or both in someembodiments. A regulator, such as an instillation regulator 155, mayalso be fluidly coupled to the solution source 145 and the dressing 110to ensure proper dosage of instillation solution (e.g. saline) to atissue site. For example, the instillation regulator 155 may comprise apiston that can be pneumatically actuated by the negative-pressuresource 105 to draw instillation solution from the solution source duringa negative-pressure interval and to instill the solution to a dressingduring a venting interval. Additionally or alternatively, the controller120 may be coupled to the negative-pressure source 105, thepositive-pressure source 150, or both, to control dosage of instillationsolution to a tissue site. In some embodiments, the instillationregulator 155 may also be fluidly coupled to the negative-pressuresource 105 through the dressing 110, as illustrated in the example ofFIG. 1.

Some components of the therapy system 100 may be housed within or usedin conjunction with other components, such as sensors, processing units,alarm indicators, memory, databases, software, display devices, or userinterfaces that further facilitate therapy. For example, in someembodiments, the negative-pressure source 105 may be combined with thesolution source 145, the controller 120, and other components into atherapy unit.

In general, components of the therapy system 100 may be coupled directlyor indirectly. For example, the negative-pressure source 105 may bedirectly coupled to the container 115 and may be indirectly coupled tothe dressing 110 through the container 115. Coupling may include fluid,mechanical, thermal, electrical, or chemical coupling (such as achemical bond), or some combination of coupling in some contexts. Forexample, the negative-pressure source 105 may be electrically coupled tothe controller 120 fluidly coupled to one or more distributioncomponents to provide a fluid path to a tissue site. In someembodiments, components may also be coupled by virtue of physicalproximity, being integral to a single structure, or being formed fromthe same piece of material.

A distribution component is preferably detachable and may be disposable,reusable, or recyclable. The dressing 110 and the container 115 areillustrative of distribution components. A fluid conductor is anotherillustrative example of a distribution component. A “fluid conductor,”in this context, broadly includes a tube, pipe, hose, conduit, or otherstructure with one or more lumina or open pathways adapted to convey afluid between two ends. Typically, a tube is an elongated, cylindricalstructure with some flexibility, but the geometry and rigidity may vary.Moreover, some fluid conductors may be molded into or otherwiseintegrally combined with other components. Distribution components mayalso include or comprise interfaces or fluid ports to facilitatecoupling and de-coupling other components. In some embodiments, forexample, a dressing interface may facilitate coupling a fluid conductorto the dressing 110. For example, such a dressing interface may be aSENSAT.R.A.C.™ Pad available from Kinetic Concepts, Inc. of San Antonio,Tex.

A negative-pressure supply, such as the negative-pressure source 105,may be a reservoir of air at a negative pressure or may be a manual orelectrically-powered device. Examples of a suitable negative-pressuresupply may include a vacuum pump, a suction pump, a wall suction portavailable at many healthcare facilities, or a micro-pump. “Negativepressure” generally refers to a pressure less than a local ambientpressure, such as the ambient pressure in a local environment externalto a sealed therapeutic environment. In many cases, the local ambientpressure may also be the atmospheric pressure at which a tissue site islocated. Alternatively, the pressure may be less than a hydrostaticpressure associated with tissue at the tissue site. Unless otherwiseindicated, values of pressure stated herein are gauge pressures.References to increases in negative pressure typically refer to adecrease in absolute pressure, while decreases in negative pressuretypically refer to an increase in absolute pressure. While the amountand nature of negative pressure applied to a tissue site may varyaccording to therapeutic requirements, the pressure is generally a lowvacuum, also commonly referred to as a rough vacuum, between −5 mm Hg(−667 Pa) and −500 mm Hg (−66.7 kPa). Common therapeutic ranges arebetween −50 mm Hg (−6.7 kPa) and −300 mm Hg (−39.9 kPa).

The container 115 is representative of a container, canister, pouch, orother storage component, which can be used to manage exudates and otherfluids withdrawn from a tissue site. In many environments, a rigidcontainer may be preferred or required for collecting, storing, anddisposing of fluids. In other environments, fluids may be properlydisposed of without rigid container storage, and a re-usable containercould reduce waste and costs associated with negative-pressure therapy.

A controller, such as the controller 120, may be a microprocessor orcomputer programmed to operate one or more components of the therapysystem 100, such as the negative-pressure source 105. In someembodiments, for example, the controller 120 may be a microcontroller,which generally comprises an integrated circuit containing a processorcore and a memory programmed to directly or indirectly control one ormore operating parameters of the therapy system 100. Operatingparameters may include the power applied to the negative-pressure source105, the pressure generated by the negative-pressure source 105, or thepressure distributed to the tissue interface 135, for example. Thecontroller 120 is also preferably configured to receive one or moreinput signals, such as a feedback signal, and programmed to modify oneor more operating parameters based on the input signals.

Sensors, such as the first sensor 125 and the second sensor, 130 aregenerally known in the art as any apparatus operable to detect ormeasure a physical phenomenon or property, and generally provide asignal indicative of the phenomenon or property that is detected ormeasured. For example, the first sensor 125 and the second sensor 130may be configured to measure one or more operating parameters of thetherapy system 100. In some embodiments, the first sensor 125 may be atransducer configured to measure pressure in a pneumatic pathway andconvert the measurement to a signal indicative of the pressure measured.In some embodiments, for example, the first sensor 125 may be apiezo-resistive strain gauge. The second sensor 130 may optionallymeasure operating parameters of the negative-pressure source 105, suchas a voltage or current, in some embodiments. Preferably, the signalsfrom the first sensor 125 and the second sensor 130 are suitable as aninput signal to the controller 120, but some signal conditioning may beappropriate in some embodiments. For example, the signal may need to befiltered or amplified before it can be processed by the controller 120.Typically, the signal is an electrical signal, but may be represented inother forms, such as an optical signal.

The tissue interface 135 can be generally adapted to partially or fullycontact a tissue site. The tissue interface 135 may take many forms andmay have many sizes, shapes, or thicknesses, depending on a variety offactors, such as the type of treatment being implemented or the natureand size of a tissue site. For example, the size and shape of the tissueinterface 135 may be adapted to the contours of deep and irregularshaped tissue sites. Moreover, any or all of the surfaces of the tissueinterface 135 may have projections or an uneven, coarse, or jaggedprofile that can induce strains and stresses on a tissue site, which canpromote granulation at the tissue site.

In some embodiments, the tissue interface 135 may comprise or consistessentially of a manifold. A “manifold” in this context generallyincludes any substance or structure providing a plurality of pathwaysadapted to collect or distribute fluid across a tissue site underpressure. For example, a manifold may be adapted to receive negativepressure from a source and distribute negative pressure through multipleapertures across a tissue site, which may have the effect of collectingfluid from across a tissue site and drawing the fluid toward the source.In some embodiments, the fluid path may be reversed or a secondary fluidpath may be provided to facilitate delivering fluid, such as fluid froma source of instillation solution, across a tissue site.

In some illustrative embodiments, the pathways of a manifold may beinterconnected to improve distribution or collection of fluids across atissue site. In some illustrative embodiments, a manifold may be aporous foam material having interconnected cells or pores. For example,open-cell foam, porous tissue collections, and other porous materialsuch as gauze or felted mat generally include pores, edges, and/or wallsadapted to form interconnected fluid channels. Liquids, gels, and otherfoams may also include, or be cured to include, apertures and fluidpathways. In some embodiments, a manifold may additionally oralternatively comprise projections that form interconnected fluidpathways. For example, a manifold may be molded to provide surfaceprojections that define interconnected fluid pathways.

The average pore size of foam may vary according to needs of aprescribed therapy. For example, in some embodiments, the tissueinterface 135 may comprise or consist essentially of foam having poresizes in a range of 400-600 microns. The tensile strength of the tissueinterface 135 may also vary according to needs of a prescribed therapy.For example, the tensile strength of foam may be increased forinstillation of topical treatment solutions. In some examples, thetissue interface 135 may be reticulated polyurethane foam such as foundin GRANUFOAM™ dressing or V.A.C. VERAFLO™ dressing, both available fromKinetic Concepts, Inc. of San Antonio, Tex.

The tissue interface 135 may further promote granulation at a tissuesite when pressure within the sealed therapeutic environment is reduced.For example, any or all of the surfaces of the tissue interface 135 mayhave an uneven, coarse, or jagged profile that can induce microstrainsand stresses at a tissue site if negative pressure is applied throughthe tissue interface 135.

In some embodiments, the tissue interface 135 may be constructed frombioresorbable materials. Suitable bioresorbable materials may include,without limitation, a polymeric blend of polylactic acid (PLA) andpolyglycolic acid (PGA). The polymeric blend may also include, withoutlimitation, polycarbonates, polyfumarates, and capralactones. The tissueinterface 135 may further serve as a scaffold for new cell-growth, or ascaffold material may be used in conjunction with the tissue interface135 to promote cell-growth. A scaffold is generally a substance orstructure used to enhance or promote the growth of cells or formation oftissue, such as a three-dimensional porous structure that provides atemplate for cell growth. Illustrative examples of scaffold materialsinclude calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites,carbonates, or processed allograft materials.

In some embodiments, the cover 140 may provide a bacterial barrier andprotection from physical trauma. The cover 140 may also be constructedfrom a material that can reduce evaporative losses and provide a fluidseal between two components or two environments, such as between atherapeutic environment and a local external environment. The cover 140may comprise or consist of, for example, an elastomeric film or membranethat can provide a seal adequate to maintain a negative pressure at atissue site for a given negative-pressure source. The cover 140 may havea high moisture-vapor transmission rate (MVTR) in some applications. Forexample, the MVTR may be at least 450 grams per square meter pertwenty-four hours in some embodiments, measured using an upright cuptechnique according to ASTM E96/E96M Upright Cup Method at 38° C. and10% relative humidity (RH). In some embodiments, an MVTR up to 5,000grams per square meter per twenty-four hours may provide effectivebreathability and mechanical properties.

In some example embodiments, the cover 140 may be a polymer drape, suchas a polyurethane film, that is permeable to water vapor but impermeableto liquid. Such drapes typically have a thickness in the range of 25-50microns. For permeable materials, the permeability generally should below enough that a desired negative pressure may be maintained. Forexample, the cover 140 may comprise one or more of the followingmaterials: polyurethane (PU), such as hydrophilic polyurethane;cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinylpyrrolidone; hydrophilic acrylics; silicones, such as hydrophilicsilicone elastomers; natural rubbers; polyisoprene; styrene butadienerubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber;ethylene propylene rubber; ethylene propylene diene monomer;chlorosulfonated polyethylene; polysulfide rubber; ethylene vinylacetate (EVA); co-polyester; and polyether block polymide copolymers.Such materials are commercially available as, for example, Tegaderm®drape, commercially available from 3M Company, Minneapolis Minn.;polyurethane (PU) drape, commercially available from Avery DennisonCorporation, Pasadena, Calif.; polyether block polyamide copolymer(PEBAX), for example, from Arkema S.A., Colombes, France; and Inspire2301 and Inpsire 2327 polyurethane films, commercially available fromExpopack Advanced Coatings, Wrexham, United Kingdom. In someembodiments, the cover 140 may comprise INSPIRE 2301 having an MVTR(upright cup technique) of 2600 g/m²/24 hours and a thickness of about30 microns.

An attachment device may be used to attach the cover 140 to anattachment surface, such as undamaged epidermis, a gasket, or anothercover. The attachment device may take many forms. For example, anattachment device may be a medically-acceptable, pressure-sensitiveadhesive configured to bond the cover 140 to epidermis around a tissuesite. In some embodiments, for example, some or all of the cover 140 maybe coated with an adhesive, such as an acrylic adhesive, which may havea coating weight of 25-65 grams per square meter (g.s.m.). Thickeradhesives, or combinations of adhesives, may be applied in someembodiments to improve the seal and reduce leaks. Other exampleembodiments of an attachment device may include a double-sided tape,paste, hydrocolloid, hydrogel, silicone gel, or organogel.

The solution source 145 may also be representative of a container,canister, pouch, bag, or other storage component, which can provide asolution for instillation therapy. Compositions of solutions may varyaccording to a prescribed therapy, but examples of solutions that may besuitable for some prescriptions include hypochlorite-based solutions,silver nitrate (0.5%), sulfur-based solutions, biguanides, cationicsolutions, and isotonic solutions.

FIG. 2 is a graph illustrating additional details of an example controlmode that may be associated with some embodiments of the controller 120.In some embodiments, the controller 120 may have a continuous pressuremode, in which the negative-pressure source 105 is operated to provide aconstant target negative pressure, as indicated by line 205 and line210, for the duration of treatment or until manually deactivated.Additionally or alternatively, the controller may have an intermittentpressure mode, as illustrated in the example of FIG. 2. In FIG. 2, thex-axis represents time, and the y-axis represents negative pressuregenerated by the negative-pressure source 105 over time. In the exampleof FIG. 2, the controller 120 can operate the negative-pressure source105 to cycle between a target pressure and atmospheric pressure. Forexample, the target pressure may be set at a value of 125 mmHg, asindicated by line 205, for a specified period of time (e.g., 5 min),followed by a specified period of time (e.g., 2 min) of deactivation, asindicated by the gap between the solid lines 215 and 220. The cycle canbe repeated by activating the negative-pressure source 105, as indicatedby line 220, which can form a square wave pattern between the targetpressure and atmospheric pressure.

In some example embodiments, the increase in negative-pressure fromambient pressure to the target pressure may not be instantaneous. Forexample, the negative-pressure source 105 and the dressing 110 may havean initial rise time, as indicated by the dashed line 225. The initialrise time may vary depending on the type of dressing and therapyequipment being used. For example, the initial rise time for one therapysystem may be in a range of about 20-30 mmHg/second and in a range ofabout 5-10 mmHg/second for another therapy system. If the therapy system100 is operating in an intermittent mode, the repeating rise time, asindicated by the solid line 220, may be a value substantially equal tothe initial rise time as indicated by the dashed line 225.

FIG. 3 is a graph illustrating additional details that may be associatedwith another example pressure control mode in some embodiments of thetherapy system 100. In FIG. 3, the x-axis represents time and the y-axisrepresents negative pressure generated by the negative-pressure source105. The target pressure in the example of FIG. 3 can vary with time ina dynamic pressure mode. For example, the target pressure may vary inthe form of a triangular waveform, varying between a negative pressureof 50 and 125 mmHg with a rise time 305 set at a rate of +25 mmH g/min.and a descent time 310 set at −25 mmH g/min. In other embodiments of thetherapy system 100, the triangular waveform may vary between negativepressure of 25 and 125 mmHg with a rise time 305 set at a rate of +30mmH g/min and a descent time 310 set at −30 mmH g/min.

In some embodiments, the controller 120 may control or determine avariable target pressure in a dynamic pressure mode, and the variabletarget pressure may vary between a maximum and minimum pressure valuethat may be set as an input prescribed by an operator as the range ofdesired negative pressure. The variable target pressure may also beprocessed and controlled by the controller 120, which can vary thetarget pressure according to a predetermined waveform, such as atriangular waveform, a sine waveform, or a saw-tooth waveform. In someembodiments, the waveform may be set by an operator as the predeterminedor time-varying negative pressure desired for therapy.

FIG. 4 is an assembly view of an example of the dressing 110 of FIG. 1,illustrating additional details that may be associated with someembodiments in which the tissue interface 135 comprises more than onelayer. In the example of FIG. 2, the tissue interface 135 comprises amanifold 405, a polymer film 410, and a gel layer 415. In someembodiments, the manifold 405 may be disposed adjacent to the polymerfilm 410, and the gel layer 415 may be disposed adjacent to the polymerfilm 410 opposite the manifold 405. For example, the manifold 405, thepolymer film 410, and the gel layer 415 may be stacked so that themanifold 405 is in contact with the polymer film 410, and the polymerfilm 410 is in contact with the manifold 405 and the gel layer 415. Oneor more of the manifold 405, the polymer film 410, and the gel layer 415may also be bonded to an adjacent layer in some embodiments.

The manifold 405 may comprise or consist essentially of a means forcollecting or distributing fluid across the tissue interface 135 underpressure. For example, the manifold 405 may be adapted to receivenegative pressure from a source and distribute negative pressure throughmultiple apertures across the tissue interface 135, which may have theeffect of collecting fluid from across a tissue site and drawing thefluid toward the source. In some embodiments, the fluid path may bereversed or a secondary fluid path may be provided to facilitatedelivering fluid, such as from a source of instillation solution, acrossthe tissue interface 135.

In some illustrative embodiments, the manifold 405 may comprise aplurality of pathways, which can be interconnected to improvedistribution or collection of fluids. In some embodiments, the manifold405 may comprise or consist essentially of a porous material havinginterconnected fluid pathways. For example, open-cell foam, poroustissue collections, and other porous material such as gauze or feltedmat generally include pores, edges, and/or walls adapted to forminterconnected fluid channels. Liquids, gels, and other foams may alsoinclude or be cured to include apertures and fluid pathways. In someembodiments, the manifold 405 may additionally or alternatively compriseprojections that form interconnected fluid pathways. For example, themanifold 405 may be molded to provide surface projections that defineinterconnected fluid pathways. Any or all of the surfaces of themanifold 405 may have an uneven, coarse, or jagged profile.

In some embodiments, the manifold 405 may comprise or consistessentially of reticulated foam having pore sizes and free volume thatmay vary according to needs of a prescribed therapy. For example,reticulated foam having a free volume of at least 90% may be suitablefor many therapy applications, and foam having an average pore size in arange of 400-600 microns (40-50 pores per inch) may be particularlysuitable for some types of therapy. The tensile strength of the manifold405 may also vary according to needs of a prescribed therapy. Forexample, the tensile strength of the manifold 405 may be increased forinstillation of topical treatment solutions. The 25% compression loaddeflection of the manifold 405 may be at least 0.35 pounds per squareinch, and the 65% compression load deflection may be at least 0.43pounds per square inch. In some embodiments, the tensile strength of themanifold 405 may be at least 10 pounds per square inch. The manifold 405may have a tear strength of at least 2.5 pounds per inch. In someembodiments, the manifold 405 may be foam comprised of polyols such aspolyester or polyether, isocyanate such as toluene diisocyanate, andpolymerization modifiers such as amines and tin compounds. In onenon-limiting example, the manifold 405 may be a reticulated polyurethaneether foam such as used in GRANUFOAM™ dressing or V.A.C. VERAFLO™dressing, both available from KCI of San Antonio, Tex.

The thickness of the manifold 405 may also vary according to needs of aprescribed therapy. For example, the thickness of the manifold 405 maybe decreased to relieve stress on other layers and to reduce tension onperipheral tissue. The thickness of the manifold 405 can also affect theconformability of the manifold 405. In some embodiments, a thickness ina range of about 5 millimeters to 10 millimeters may be suitable.

The polymer film 410 may comprise or consist essentially of a means forcontrolling or managing fluid flow. In some embodiments, the polymerfilm 410 may comprise or consist essentially of a liquid-impermeable,elastomeric polymer. The polymer film 410 may also have a smooth ormatte surface texture in some embodiments. A glossy or shiny finishbetter or equal to a grade B3 according to the SPI (Society of thePlastics Industry) standards may be particularly advantageous for someapplications. In some embodiments, variations in surface height may belimited to acceptable tolerances. For example, the surface of thepolymer film 410 may have a substantially flat surface, with heightvariations limited to 0.2 millimeters over a centimeter.

In some embodiments, the polymer film 410 may be hydrophobic. Thehydrophobicity of the polymer film 410 may vary, and may have a contactangle with water of at least ninety degrees in some embodiments. In someembodiments the polymer film 410 may have a contact angle with water ofno more than 150 degrees. For example, in some embodiments, the contactangle of the polymer film 410 may be in a range of at least 90 degreesto about 120 degrees or in a range of at least 120 degrees to 150degrees. Water contact angles can be measured using any standardapparatus. Although manual goniometers can be used to visuallyapproximate contact angles, contact angle measuring instruments canoften include an integrated system involving a level stage, liquiddropper such as a syringe, camera, and software designed to calculatecontact angles more accurately and precisely, among other things.Non-limiting examples of such integrated systems may include the FTÅ125,FTÅ200, FTÅ2000 , and FTÅ4000 systems, all commercially available fromFirst Ten Angstroms, Inc., of Portsmouth, Va., and the DTA25, DTA30, andDTA100 systems, all commercially available from Kruss GmbH of Hamburg,Germany. Unless otherwise specified, water contact angles herein aremeasured using deionized and distilled water on a level sample surfacefor a sessile drop added from a height of no more than 5 cm in air at20-25° C. and 20-50% relative humidity. Contact angles reported hereinrepresent averages of 5-9 measured values, discarding both the highestand lowest measured values. The hydrophobicity of the polymer film 410may be further enhanced with a hydrophobic coating of other materials,such as silicones and fluorocarbons, either as coated from a liquid orplasma coated.

The polymer film 410 may also be suitable for welding to other layers,including the manifold 405. For example, the polymer film 410 may beadapted for welding to polyurethane foams using heat, radio frequency(RF) welding, or other methods to generate heat, such as ultrasonicwelding. RF welding may be particularly suitable for more polarmaterials, such as polyurethane, polyamides, polyesters and acrylates.Sacrificial polar interfaces may be used to facilitate RF welding ofless polar film materials, such as polyethylene.

The area density of the polymer film 410 may vary according to aprescribed therapy or application. In some embodiments, an area densityof less than 40 grams per square meter may be suitable, and an areadensity of about 20-30 grams per square meter may be particularlyadvantageous for some applications.

In some embodiments, for example, the polymer film 410 may comprise orconsist essentially of a hydrophobic polymer, such as a polyethylenefilm. The simple and inert structure of polyethylene can provide asurface that interacts little, if at all, with biological tissues andfluids. Such a surface may encourage the free flow of liquid and lowadherence, which can be particularly advantageous for many applications.More polar films suitable for laminating to a polyethylene film includepolyamide, co-polyesters, ionomers, and acrylics. To aid in the bondbetween a polyethylene and polar film, tie layers may be used, such asethylene vinyl acetate or modified polyurethanes. An ethyl methylacrylate (EMA) film may also have suitable hydrophobic and weldingproperties for some configurations.

As illustrated in the example of FIG. 4, the polymer film 410 may haveone or more fluid restrictions 420, which can be distributed uniformlyor randomly across the polymer film 410. The fluid restrictions 420 maybe bi-directional and pressure-responsive. For example, the fluidrestrictions 420 can generally comprise or consist essentially of anelastic passage through the polymer film 410 that is normally unstrainedto substantially reduce liquid flow, and the elastic passage can expandin response to a pressure gradient. In some embodiments, the fluidrestrictions 420 may comprise or consist essentially of perforations inthe polymer film 410. Perforations may be formed by removing materialfrom the polymer film 410. For example, perforations may be formed bycutting through the polymer film 410, which may also deform the edges ofthe perforations in some embodiments. In the absence of a pressuregradient across the perforations, the passages may be sufficiently smallto form a seal or flow restriction, which can substantially reduce orprevent liquid flow. Additionally or alternatively, one or more of thefluid restrictions 420 may be an elastomeric valve that is normallyclosed when unstrained to substantially prevent liquid flow and can openin response to a pressure gradient. A fenestration in the polymer film410 may be a suitable valve for some applications. Fenestrations mayalso be formed by removing material from the polymer film 410, but theamount of material removed and the resulting dimensions of thefenestrations may be up to an order of magnitude less than perforations,and may not deform the edges.

For example, some embodiments of the fluid restrictions 420 may compriseor consist essentially of one or more slots or combinations of slots inthe polymer film 410. In some examples, the fluid restrictions 420 maycomprise or consist of linear slots having a length less than 4millimeters and a width less than 1 millimeter. The length may be atleast 2 millimeters, and the width may be at least 0.4 millimeters insome embodiments. A length of about 3 millimeters and a width of about0.8 millimeter may be particularly suitable for many applications. Atolerance of about 0.1 millimeter may also be acceptable. Slots of suchconfigurations may function as imperfect valves that substantiallyreduce liquid flow in a normally closed or resting state. For example,such slots may form a flow restriction without being completely closedor sealed. The slots can expand or open wider in response to a pressuregradient to allow increased liquid flow.

The gel layer 415 may comprise or consist essentially of a fixationlayer having a tacky surface and may be formed from a soft polymersuitable for providing a fluid seal with a tissue site. The gel layer415 may be a polymer gel having a coating weight of about 450 g.s.m.,and may have a substantially flat surface in some examples. For example,the gel layer 415 may comprise, without limitation, a silicone gel,hydrocolloid, hydrogel, polyurethane gel, polyolefin gel, hydrogenatedstyrenic copolymer gel, or a foamed gel. In some embodiments, the gellayer 415 may have a thickness between about 200 microns (μm) and about1000 microns (μm). In some embodiments, the gel layer 415 may have ahardness between about 5 Shore OO and about 80 Shore OO. Further, thegel layer 415 may be comprised of hydrophobic or hydrophilic materials.

The gel layer 415 may have a periphery 425 surrounding or around aninterior portion 430, and apertures 435 disposed through the periphery425 and the interior portion 430. The interior portion 430 maycorrespond to a surface area of the manifold 405 in some examples. Thegel layer 415 may also have corners 440 and edges 445. The corners 440and the edges 445 may be part of the periphery 425. The gel layer 415may have an interior border 450 around the interior portion 430,disposed between the interior portion 430 and the periphery 425. Theinterior border 450 may be substantially free of the apertures 435, asillustrated in the example of FIG. 4. In some examples, as illustratedin FIG. 4, the interior portion 430 may be symmetrical and centrallydisposed in the gel layer 415.

The apertures 435 may have a uniform distribution pattern or may berandomly distributed in the gel layer 415. The apertures 435 in the gellayer 415 may have many shapes, including circles, squares, stars,ovals, polygons, slits, complex curves, rectilinear shapes, triangles,for example, or may have some combination of such shapes.

Each of the apertures 435 may have uniform or similar geometricproperties. For example, in some embodiments, each of the apertures 435may be circular apertures, having substantially the same diameter. Insome embodiments, the diameter of each of the apertures 435 may bebetween about 1 millimeter and about 50 millimeters. In otherembodiments, the diameter of each of the apertures 435 may be betweenabout 1 millimeter and about 20 millimeters.

In other embodiments, geometric properties of the apertures 435 mayvary. For example, the diameter of the apertures 435 may vary dependingon the position of the apertures 435 in the gel layer 415, asillustrated in FIG. 4. In some embodiments, the diameter of theapertures 435 in the periphery 425 of the gel layer 415 may be largerthan the diameter of the apertures 435 in the interior portion 430 ofthe gel layer 415. For example, in some embodiments, the apertures 435disposed in the periphery 425 may have a diameter between about 9.8millimeters and about 10.2 millimeters. In some embodiments, theapertures 435 disposed in the corners 440 may have a diameter betweenabout 7.75 millimeters and about 8.75 millimeters. In some embodiments,the apertures 435 disposed in the interior portion 430 may have adiameter between about 1.8 millimeters and about 2.2 millimeters. Inother embodiments, the apertures 435 disposed in the interior portion430 may be slots having a width of about 2 millimeters and a length ofabout 3 millimeters.

At least one of the apertures 435 in the periphery 425 of the gel layer415 may be positioned at the edges 445 of the periphery 425 and may havean interior cut open or exposed at the edges 445 that is in fluidcommunication in a lateral direction with the edges 445. The lateraldirection may refer to a direction toward the edges 445 and in the sameplane as the gel layer 415. As shown in the example of FIG. 4, theapertures 435 in the periphery 425 may be positioned proximate to or atthe edges 445 and in fluid communication in a lateral direction with theedges 445. The apertures 435 positioned proximate to or at the edges 445may be spaced substantially equidistant around the periphery 425 asshown in the example of FIG. 4. Alternatively, the spacing of theapertures 435 proximate to or at the edges 445 may be irregular.

In the example of FIG. 4, the dressing 110 may further include anattachment device, such as an adhesive 455. The adhesive 455 may be, forexample, a medically-acceptable, pressure-sensitive adhesive thatextends about a periphery, a portion, or the entire cover 140. In someembodiments, for example, the adhesive 455 may be an acrylic adhesivehaving a coating weight between 25-65 grams per square meter (g.s.m.).Thicker adhesives, or combinations of adhesives, may be applied in someembodiments to improve the seal and reduce leaks. The adhesive 455 maybe a layer having substantially the same shape as the periphery 425. Insome embodiments, such a layer of the adhesive 455 may be continuous ordiscontinuous. Discontinuities in the adhesive 455 may be provided byapertures or holes (not shown) in the adhesive 455. The apertures orholes in the adhesive 455 may be formed after application of theadhesive 455 or by coating the adhesive 455 in patterns on a carrierlayer, such as, for example, a side of the cover 140. Apertures or holesin the adhesive 455 may also be sized to enhance the moisture-vaportransfer rate of the dressing 110 in some example embodiments.

As illustrated in the example of FIG. 4, in some embodiments, a releaseliner 460 may be attached to or positioned adjacent to the gel layer 415to protect the adhesive 455 prior to use. The release liner 460 may alsoprovide stiffness to assist with, for example, deployment of thedressing 110. Examples of the release liner 460 may include a castingpaper, a film, or polyethylene. Further, in some embodiments, therelease liner 460 may be a polyester material such as polyethyleneterephthalate (PET), or similar polar semi-crystalline polymer. The useof a polar semi-crystalline polymer for the release liner 460 maysubstantially preclude wrinkling or other deformation of the dressing110. For example, the polar semi-crystalline polymer may be highlyorientated and resistant to softening, swelling, or other deformationthat may occur when brought into contact with components of the dressing110 or when subjected to temperature or environmental variations, orsterilization. In some embodiments, the release liner 460 may have asurface texture that may be imprinted on an adjacent layer, such as thegel layer 415. Further, a release agent may be disposed on a side of therelease liner 460 that is configured to contact the gel layer 415. Forexample, the release agent may be a silicone coating and may have arelease factor suitable to facilitate removal of the release liner 460by hand and without damaging or deforming the dressing 110. In someembodiments, the release agent may be a fluorocarbon or afluorosilicone, for example. In other embodiments, the release liner 460may be uncoated or otherwise used without a release agent.

FIG. 4 also illustrates one example of a fluid conductor 465 and adressing interface 470. As shown in the example of FIG. 4, the fluidconductor 465 may be a flexible tube, which can be fluidly coupled onone end to the dressing interface 470. The dressing interface 470 may bean elbow connector, as shown in the example of FIG. 4, which can beplaced over an aperture 475 in the cover 140 to provide a fluid pathbetween the fluid conductor 465 and the tissue interface 135.

FIG. 5 is a schematic view of an example of the polymer film 410,illustrating additional details that may be associated with someembodiments. As illustrated in the example of FIG. 5, the fluidrestrictions 420 may each consist essentially of one or more linearslots having a length of about 3 millimeters. FIG. 5 additionallyillustrates an example of a uniform distribution pattern of the fluidrestrictions 420. In FIG. 5, the fluid restrictions 420 aresubstantially coextensive with the polymer film 410 and are distributedacross the polymer film 410 in a grid of parallel rows and columns, inwhich the slots are also mutually parallel to each other. In someembodiments, the rows may be spaced about 3 millimeters on center, andthe fluid restrictions 420 within each of the rows may be spaced about 3millimeters on center, as illustrated in the example of FIG. 5. Thefluid restrictions 420 in adjacent rows may be aligned or offset. Forexample, adjacent rows may be offset, as illustrated in FIG. 5, so thatthe fluid restrictions 420 are aligned in alternating rows and separatedby about 6 millimeters. The spacing of the fluid restrictions 420 mayvary in some embodiments to increase the density of the fluidrestrictions 420 according to therapeutic requirements.

FIG. 6 is a schematic view of an example configuration of the apertures435, illustrating additional details that may be associated with someembodiments of the gel layer 415. In some embodiments, the apertures 435illustrated in FIG. 6 may be associated only with the interior portion430. In the example of FIG. 6, the apertures 435 are generally circularand have a diameter of about 2 millimeters. FIG. 6 also illustrates anexample of a uniform distribution pattern of the apertures 435. In FIG.6, the apertures 435 are distributed in a grid of parallel rows andcolumns. Within each row and column, the apertures 435 may beequidistant from each other, as illustrated in the example of FIG. 6.FIG. 6 illustrates one example configuration of the apertures 435 thatmay be particularly suitable for many applications, in which theapertures 435 are spaced about 6 millimeters apart along each row andcolumn, with a 3 millimeter offset.

FIG. 7 is a schematic view of an example of the gel layer 415 having theconfiguration of apertures 435 of FIG. 6 overlaid on the polymer film410 of FIG. 5, illustrating additional details that may be associatedwith some example embodiments of the tissue interface 135. For example,as illustrated in FIG. 7, the fluid restrictions 420 may be aligned,overlapping, in registration with, or otherwise fluidly coupled to theapertures 435 in some embodiments. In some embodiments, one or more ofthe fluid restrictions 420 may be registered with the apertures 435 onlyin the interior portion 430 or only partially registered with theapertures 435. The fluid restrictions 420 in the example of FIG. 7 aregenerally configured so that each of the fluid restrictions 420 isregistered with only one of the apertures 435. In other examples, one ormore of the fluid restrictions 420 may be registered with more than oneof the apertures 435. For example, any one or more of the fluidrestrictions 420 may be a perforation or a fenestration that extendsacross two or more of the apertures 435. Additionally or alternatively,one or more of the fluid restrictions 420 may not be registered with anyof the apertures 435.

As illustrated in the example of FIG. 7, the apertures 435 may be sizedto expose a portion of the polymer film 410, the fluid restrictions 420,or both through the gel layer 415. In some embodiments, each of theapertures 435 may be sized to expose no more than two of the fluidrestrictions 420. In some examples, the length of each of the fluidrestrictions 420 may be substantially equal to or less than the diameterof each of the apertures 435. In some embodiments, the averagedimensions of the fluid restrictions 420 are substantially similar tothe average dimensions of the apertures 435. For example, the apertures435 may be elliptical in some embodiments, and the length of each of thefluid restrictions 420 may be substantially equal to the major axis orthe minor axis. In some embodiments, though, the dimensions of the fluidrestrictions 420 may exceed the dimensions of the apertures 435, and thesize of the apertures 435 may limit the effective size of the fluidrestrictions 420 exposed to the lower surface of the dressing 110.

FIG. 8 is a flow diagram illustrating an example method 800 ofmanufacturing some components of the dressing 110. In the example ofFIG. 8, a first layer of the dressing 110 can be perforated at 805. Forexample, the first layer may be the gel layer 415, and the apertures 435may be formed by a laser or by other suitable techniques for forming theapertures 435 in the gel layer 415. The first layer with perforationscan be placed on an assembly substrate at 810. For example, the firstlayer can be held on a web and then on a roll or liner. An index of theperforations may be created at 815, and the laser or other cutting meansmay be calibrated at 820 based on the index. A second layer may becoupled to the first layer at 825. The second layer may be the polymerfilm 410, for example, which may be cut to a preferred size and shapeand then loaded and fixed to the gel layer 415. Slots (or slits) may becut in the second layer through the apertures in the first layer at 830.For example, a combined laminate of the polymer film 410 and the gellayer 415 may be presented to a laser, where the laser calibrates theposition of a laser mask to the underside of the combined laminate,referencing the apertures 435 to calibrate its position. The laser canthen be fired, creating the fluid restrictions 420 in the polymer film410, centrally registered within the apertures 435 and having a lengthsubstantially equal to or less than the length or diameter of each ofthe apertures 435. In some embodiments, the fluid restrictions 420 mayhave a length slightly longer than the length or diameter of theapertures 435 without affecting the performance of the dressing 110.

One or more of the components of the dressing 110 may additionally betreated with an antimicrobial agent in some embodiments. For example,the manifold 405 may be a foam, mesh, or non-woven coated with anantimicrobial agent. In some embodiments, the manifold 405 may compriseantimicrobial elements, such as fibers coated with an antimicrobialagent. Additionally or alternatively, some embodiments of the polymerfilm 410 may be a polymer coated or mixed with an antimicrobial agent.In other examples, the fluid conductor 465 may additionally oralternatively be treated with one or more antimicrobial agents. Suitableantimicrobial agents may include, for example, metallic silver, PHMB,iodine or its complexes and mixes such as povidone iodine, copper metalcompounds, chlorhexidine, or some combination of these materials.

Individual components of the dressing 110 may be bonded or otherwisesecured to one another with a solvent or non-solvent adhesive or withthermal welding, for example, without adversely affecting fluidmanagement. Further, the manifold 405 or the polymer film 410 may becoupled to the border 450 of the gel layer 415 in any suitable manner,such as with a weld or an adhesive, for example.

The manifold 405, the polymer film 410, the gel layer 415, the cover140, or various combinations may be assembled before application or insitu. For example, the cover 140 may be laminated to the manifold 405,and the polymer film 410 may be laminated to the manifold 405 oppositethe cover 140 in some embodiments. The gel layer 415 may also be coupledto the polymer film 410 opposite the manifold 405 in some embodiments.In some embodiments, one or more layers of the tissue interface 135 maycoextensive. For example, the manifold 405 may be coextensive with thepolymer film 410, as illustrated in the embodiment of FIG. 4. In someembodiments, the dressing 110 may be provided as a single, compositedressing. For example, the gel layer 415 may be coupled to the cover 140to enclose the manifold 405 and the polymer film 410, wherein the gellayer 415 is configured to face a tissue site.

In use, the release liner 460 (if included) may be removed to expose thegel layer 415, which may be placed within, over, on, or otherwiseproximate to a tissue site, particularly a surface tissue site andadjacent epidermis. The gel layer 415 and the polymer film 410 may beinterposed between the manifold 405 and a tissue site, which cansubstantially reduce or eliminate adverse interaction with the manifold405. For example, the gel layer 415 may be placed over a surface wound(including edges of the wound) and undamaged epidermis to prevent directcontact with the manifold 405. Treatment of a surface wound, orplacement of the dressing 110 on a surface wound, includes placing thedressing 110 immediately adjacent to the surface of the body orextending over at least a portion of the surface of the body. Treatmentof a surface wound does not include placing the dressing 110 whollywithin the body or wholly under the surface of the body, such as placinga dressing within an abdominal cavity. In some applications, theinterior portion 430 of the gel layer 415 may be positioned adjacent to,proximate to, or covering a tissue site. In some applications, at leastsome portion of the polymer film 410, the fluid restrictions 420, orboth may be exposed to a tissue site through the gel layer 415. Theperiphery 425 of the gel layer 415 may be positioned adjacent to orproximate to tissue around or surrounding the tissue site. The gel layer415 may be sufficiently tacky to hold the dressing 110 in position,while also allowing the dressing 110 to be removed or re-positionedwithout trauma to a tissue site.

Removing the release liner 460 can also expose the adhesive 455, and thecover 140 may be attached to an attachment surface. For example, thecover 140 may be attached to epidermis peripheral to a tissue site,around the manifold 405 and the polymer film 410. The adhesive 455 maybe in fluid communication with an attachment surface through theapertures 435 in at least the periphery 425 of the gel layer 415 in someembodiments. The adhesive 455 may also be in fluid communication withthe edges 445 through the apertures 435 exposed at the edges 445.

Once the dressing 110 is in a desired position, the adhesive 455 may bepressed through the apertures 435 to bond the dressing 110 to theattachment surface. The apertures 435 at the edges 445 may permit theadhesive 455 to flow around the edges 445 for enhancing the adhesion ofthe edges 445 to an attachment surface.

In some embodiments, apertures or holes in the gel layer 415 may besized to control the amount of the adhesive 455 in fluid communicationwith the apertures 435. For a given geometry of the corners 440, therelative sizes of the apertures 435 may be configured to maximize thesurface area of the adhesive 455 exposed and in fluid communicationthrough the apertures 435 at the corners 440. For example, as shown inFIG. 4, the edges 445 may intersect at substantially a right angle, orabout 90 degrees, to define the corners 440. In some embodiments, thecorners 440 may have a radius of about 10 millimeters. Further, in someembodiments, three of the apertures 435 having a diameter between about7.75 millimeters to about 8.75 millimeters may be positioned in atriangular configuration at the corners 440 to maximize the exposedsurface area for the adhesive 455. In other embodiments, the size andnumber of the apertures 435 in the corners 440 may be adjusted asnecessary, depending on the chosen geometry of the corners 440, tomaximize the exposed surface area of the adhesive 455. Further, theapertures 435 at the corners 440 may be fully contained within the gellayer 415, substantially precluding fluid communication in a lateraldirection exterior to the corners 440. The apertures 435 at the corners440 being fully housed within the gel layer 415 may substantiallypreclude fluid communication of the adhesive 455 exterior to the corners440 and may provide improved handling of the dressing 110 duringdeployment at a tissue site. Further, the exterior of the corners 440being substantially free of the adhesive 455 may increase theflexibility of the corners 440 to enhance comfort.

In some embodiments, the bond strength of the adhesive 455 may vary indifferent locations of the dressing 110. For example, the adhesive 455may have lower bond strength in locations adjacent to the gel layer 415where the apertures 435 are relatively larger and may have higher bondstrength where the apertures 435 are smaller. Adhesive 455 with lowerbond strength in combination with larger apertures 435 may provide abond comparable to adhesive 455 with higher bond strength in locationshaving smaller apertures 435.

The geometry and dimensions of the tissue interface 135, the cover 140,or both may vary to suit a particular application or anatomy. Forexample, the geometry or dimensions of the tissue interface 135 and thecover 140 may be adapted to provide an effective and reliable sealagainst challenging anatomical surfaces, such as an elbow or heel, atand around a tissue site. Additionally or alternatively, the dimensionsmay be modified to increase the surface area for the gel layer 415 toenhance the movement and proliferation of epithelial cells at a tissuesite and reduce the likelihood of granulation tissue in-growth.

Further, the dressing 110 may permit re-application or re-positioning toreduce or eliminate leaks, which can be caused by creases and otherdiscontinuities in the dressing 110 and a tissue site. The ability torectify leaks may increase the reliability of the therapy and reducepower consumption in some embodiments.

If not already configured, the dressing interface 470 may disposed overthe aperture 475 and attached to the cover 140. The fluid conductor 465may be fluidly coupled to the dressing interface 470 and to thenegative-pressure source 105.

In operation, the dressing 110 can provide a sealed therapeuticenvironment proximate to a tissue site, substantially isolated from theexternal environment, and the negative-pressure source 105 can reducepressure in the sealed therapeutic environment.

The fluid mechanics of using a negative-pressure source to reducepressure in another component or location, such as within a sealedtherapeutic environment, can be mathematically complex. However, thebasic principles of fluid mechanics applicable to negative-pressuretherapy and instillation are generally well-known to those skilled inthe art, and the process of reducing pressure may be describedillustratively herein as “delivering,” “distributing,” or “generating”negative pressure, for example.

In general, exudate and other fluid flow toward lower pressure along afluid path. Thus, the term “downstream” typically implies something in afluid path relatively closer to a source of negative pressure or furtheraway from a source of positive pressure. Conversely, the term “upstream”implies something relatively further away from a source of negativepressure or closer to a source of positive pressure. Similarly, it maybe convenient to describe certain features in terms of fluid “inlet” or“outlet” in such a frame of reference. This orientation is generallypresumed for purposes of describing various features and componentsherein. However, the fluid path may also be reversed in someapplications, such as by substituting a positive-pressure source for anegative-pressure source, and this descriptive convention should not beconstrued as a limiting convention.

Negative pressure applied across the tissue site through the tissueinterface 135 in the sealed therapeutic environment can inducemacro-strain and micro-strain in the tissue site. Negative pressure canalso remove exudate and other fluid from a tissue site, which can becollected in container 115.

Negative pressure applied through the tissue interface 135 can create anegative pressure differential across the fluid restrictions 420 in thepolymer film 410, which can open or expand the fluid restrictions 420from their resting state. For example, in some embodiments in which thefluid restrictions 420 may comprise substantially closed fenestrationsthrough the polymer film 410, a pressure gradient across thefenestrations can strain the adjacent material of the polymer film 410and increase the dimensions of the fenestrations to allow liquidmovement through them, similar to the operation of a duckbill valve.Opening the fluid restrictions 420 can allow exudate and other liquidmovement through the fluid restrictions 420 into the manifold 405 andthe container 115. Changes in pressure can also cause the manifold 405to expand and contract, and the interior border 450 may protect theepidermis from irritation. The polymer film 410 and the gel layer 415can also substantially reduce or prevent exposure of tissue to themanifold 405, which can inhibit growth of tissue into the manifold 405.

In some embodiments, the manifold 405 may be hydrophobic to minimizeretention or storage of liquid in the dressing 110. In otherembodiments, the manifold 405 may be hydrophilic. In an example in whichthe manifold 405 may be hydrophilic, the manifold 405 may also wickfluid away from a tissue site, while continuing to distribute negativepressure to the tissue site. The wicking properties of the manifold 405may draw fluid away from a tissue site by capillary flow or otherwicking mechanisms, for example. An example of a hydrophilic materialsuitable for some embodiments of the manifold 405 is a polyvinylalcohol, open-cell foam such as V.A.C. WHITEFOAM™ dressing availablefrom KCI of San Antonio, Tex. Other hydrophilic foams may include thosemade from polyether. Other foams that may exhibit hydrophiliccharacteristics include hydrophobic foams that have been treated orcoated to provide hydrophilicity.

If the negative-pressure source 105 is removed or turned-off, thepressure differential across the fluid restrictions 420 can dissipate,allowing the fluid restrictions 420 to move to their resting state andprevent or reduce the rate at which exudate or other liquid fromreturning to the tissue site through the polymer film 410.

In some applications, a filler may also be disposed between a tissuesite and the gel layer 415. For example, if the tissue site is a surfacewound, a wound filler may be applied interior to the periwound, and thegel layer 415 may be disposed over the periwound and the wound filler.In some embodiments, the filler may be a manifold, such as open-cellfoam. The filler may comprise or consist essentially of the samematerial as the manifold 405 in some embodiments.

Additionally or alternatively, instillation solution or other fluid maybe distributed to the dressing 110, which can increase the pressure inthe tissue interface 135. The increased pressure in the tissue interface135 can create a positive pressure differential across the fluidrestrictions 420 in the polymer film 410, which can open or expand thefluid restrictions 420 from their resting state to allow theinstillation solution or other fluid to be distributed to a tissue site.

In some embodiments, the controller 120 may receive and process datafrom one or more sensors, such as the first sensor 125. The controller120 may also control the operation of one or more components of thetherapy system 100 to manage the pressure delivered to the tissueinterface 135. In some embodiments, controller 120 may include an inputfor receiving a desired target pressure and may be programmed forprocessing data relating to the setting and inputting of the targetpressure to be applied to the tissue interface 135. In some exampleembodiments, the target pressure may be a fixed pressure value set by anoperator as the target negative pressure desired for therapy at a tissuesite and then provided as input to the controller 120. The targetpressure may vary from tissue site to tissue site based on the type oftissue forming a tissue site, the type of injury or wound (if any), themedical condition of the patient, and the preference of the attendingphysician. After selecting a desired target pressure, the controller 120can operate the negative-pressure source 105 in one or more controlmodes based on the target pressure and may receive feedback from one ormore sensors to maintain the target pressure at the tissue interface135.

The systems, apparatuses, and methods described herein may providesignificant advantages over prior art. For example, some dressings fornegative-pressure therapy can require time and skill to be properlysized and applied to achieve a good fit and seal. In contrast, someembodiments of the dressing 110 can provide a negative-pressure dressingthat is simple to apply, reducing the time to apply and remove. In someembodiments, for example, the dressing 110 may be a fully-integratednegative-pressure therapy dressing that can be applied to a tissue site(including on the periwound) in one step, without being cut to size,while still providing or improving many benefits of othernegative-pressure therapy dressings that require sizing. Such benefitsmay include good manifolding, beneficial granulation, protection of theperipheral tissue from maceration, and a low-trauma and high-seal bond.These characteristics may be particularly advantageous for surfacewounds having moderate depth and medium-to-high levels of exudate. Thedressing 110 can also be manufactured with automated processes with highthroughput, which can lower part costs. Some embodiments of the dressing110 may remain on a tissue site for at least 5 days, and someembodiments may remain for at least 7 days. Antimicrobial agents in thedressing 110 may extend the usable life of the dressing 110 by reducingor eliminating infection risks that may be associated with extended use,particularly use with infected or highly exuding wounds.

While shown in a few illustrative embodiments, a person having ordinaryskill in the art will recognize that the systems, apparatuses, andmethods described herein are susceptible to various changes andmodifications that fall within the scope of the appended claims.Moreover, descriptions of various alternatives using terms such as “or”do not require mutual exclusivity unless clearly required by thecontext, and the indefinite articles “a” or “an” do not limit thesubject to a single instance unless clearly required by the context.Components may be also be combined or eliminated in variousconfigurations for purposes of sale, manufacture, assembly, or use. Forexample, in some configurations the dressing 110, the container 115, orboth may be eliminated or separated from other components formanufacture or sale. In other example configurations, the controller 120may also be manufactured, configured, assembled, or sold independentlyof other components.

The appended claims set forth novel and inventive aspects of the subjectmatter described above, but the claims may also encompass additionalsubject matter not specifically recited in detail. For example, certainfeatures, elements, or aspects may be omitted from the claims if notnecessary to distinguish the novel and inventive features from what isalready known to a person having ordinary skill in the art. Features,elements, and aspects described in the context of some embodiments mayalso be omitted, combined, or replaced by alternative features servingthe same, equivalent, or similar purpose without departing from thescope of the invention defined by the appended claims.

What is claimed is:
 1. A method of manufacturing a dressing fornegative-pressure treatment, the method comprising: perforating a gellayer to create a plurality of apertures in the gel layer; placing apolymer film adjacent to the gel layer; and cutting a plurality of slotsin the polymer film, wherein each of the slots is cut through one of theapertures in the gel layer.
 2. The method of claim 1, wherein at leastone of the slots is centered in one of the apertures.
 3. The method ofclaim 1, wherein: each of the slots has a length not greater than alength or diameter of each of the apertures; and each of the slots has awidth not greater than a width or diameter of each of the apertures. 4.The method of claim 1, further comprising: bonding the polymer film to amanifold; and bonding a cover to the gel layer around the polymer filmand the manifold.
 5. The method of claim 1, wherein the gel layercomprises a hydrophobic gel.
 6. The method of claim 1, wherein the gellayer comprises silicone gel.
 7. The method of claim 1, wherein the gellayer has an area density less than 300 grams per square meter.
 8. Themethod of claim 1, wherein the gel layer has a hardness between about 5Shore OO and about 80 Shore OO.
 9. The method of claim 1, wherein thepolymer film is a hydrophobic polymer film.
 10. The method of claim 1,wherein the polymer film has a contact angle with water greater than 90degrees.
 11. The method of claim 1, wherein the polymer film is apolyethylene film.
 12. The method of claim 1, wherein the polymer filmis a polyethylene film having an area density of less than 30 grams persquare meter.
 13. The method of claim 1, wherein: each of the apertureshas a diameter no greater than 2 millimeters; and each of the slots hasa length no greater than the diameter of each of the apertures.
 14. Themethod of claim 1, wherein each of the apertures has a diameter greaterthan or equal to a length of each of the slots.
 15. The method of claim1, wherein: each of the apertures has a length greater than or equal toa length of each of the slots; and each of the apertures has a widthgreater than or equal to a width of each of the slots.
 16. The method ofclaim 1, wherein: the gel layer has an area density less than 300 gramsper square meter and a hardness of between about 5 Shore OO and about 80Shore OO; the polymer film has a contact angle with water greater than90 degrees and an area density of less than 30 grams per square meter;each of the slots is centered in one of the apertures; each of the slotshas a length not greater than a length or diameter of each of theapertures; and each of the slots has a width not greater than a width ordiameter of each of the apertures.